Widespread methane leakage from the sea floor on the northern US Atlantic margin

Skarke, Adam; Ruppel, C. D.; Kodis, M.; Brothers, Daniel S.; Lobecker, Elizabeth

doi:10.1038/ngeo2232

Cited by 265 publications

(328 citation statements)

References 23 publications

Supporting

Mentioning

313

Contrasting

Unclassified

Order By: Relevance

“…Apart from the Arctic, hydrate deposits in relatively shallow waters (300-700 m) in the Gulf of Mexico or along the western North Atlantic Margin will, most likely, be affected by global warming as well [Reagan and Moridis, 2007;Phrampus and Hornbach, 2012;Skarke et al, 2014]. In addition, variations in the location of ocean currents and an additional warming on decadal time scales might lead to the local dissociation of marine gas hydrates.…”

Section: Compared Tomentioning

confidence: 99%

Modeling the fate of methane hydrates under global warming

Kretschmer

Biastoch

Rüpke

et al. 2015

Global Biogeochemical Cycles

127

146

View full text Add to dashboard Cite

Large amounts of methane hydrate locked up within marine sediments are vulnerable to climate change. Changes in bottom water temperatures may lead to their destabilization and the release of methane into the water column or even the atmosphere. In a multimodel approach, the possible impact of destabilizing methane hydrates onto global climate within the next century is evaluated. The focus is set on changing bottom water temperatures to infer the response of the global methane hydrate inventory to future climate change. Present and future bottom water temperatures are evaluated by the combined use of hindcast high‐resolution ocean circulation simulations and climate modeling for the next century. The changing global hydrate inventory is computed using the parameterized transfer function recently proposed by Wallmann et al. (2012). We find that the present‐day world's total marine methane hydrate inventory is estimated to be 1146 Gt of methane carbon. Within the next 100 years this global inventory may be reduced by ∼0.03% (releasing ∼473 Mt methane from the seafloor). Compared to the present‐day annual emissions of anthropogenic methane, the amount of methane released from melting hydrates by 2100 is small and will not have a major impact on the global climate. On a regional scale, ocean bottom warming over the next 100 years will result in a relatively large decrease in the methane hydrate deposits, with the Arctic and Blake Ridge region, offshore South Carolina, being most affected.

show abstract

Section: Compared Tomentioning

confidence: 99%

Modeling the fate of methane hydrates under global warming

Kretschmer

Biastoch

Rüpke

et al. 2015

Global Biogeochemical Cycles

127

146

View full text Add to dashboard Cite

show abstract

“…Slow upward diapycnal transport of methane from bottom water into intermediate-depth waters is likely to occur during transport. While the recent discovery of extensive seafloor methane seeps aligned along the Journal of Geophysical Research: Oceans 10.1002/2015JC011084 landward limit of hydrate stability offshore North America [Skarke et al, 2014] supports the idea that the location of seafloor methane seeps is regulated by hydrate dissociation, extensive acoustic surveys offshore western Svalbard have found no evidence for southward extension of seepage along the landward limit of the GHSZ up to 20 km to the south of the study area [Sahling et al, 2014]. However, a single depth profile $30 km to the south of our study area revealed methane concentrations increasing with depth to a bottom water maximum of 40 nM (supporting information Figure S3), and elevated methane concentrations in water on the upper slope $150 km south of our study area have previously been reported [Damm et al, 2005].…”

Section: Sources Of Methane To the Upper Water Columnmentioning

confidence: 99%

“…The oceans are therefore considered to make a minor contribution to the global atmospheric methane budget [Kirschke et al, 2013], with inputs from surface seawater only occurring in localized regions of surface supersaturation, for example, where methane is transported directly to the sea surface in the gas phase. However, new sites of seafloor methane seepage continue to be discovered [e.g., R€ omer et al, 2014;Skarke et al, 2014], and recent studies suggest that sea to air methane fluxes at some locations may be far higher than previously thought [e.g., Shakhova et al, 2010a]. Seepage of methane from seafloor sediments in the Arctic Ocean has been linked to release from temperature-sensitive shallow marine sediment reservoirs, including permafrost and methane hydrate [Berndt et al, 2014;Ferre et al, 2012;Sahling et al, 2014;Shakhova et al, 2014;Westbrook et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard

et al. 2015

View full text Add to dashboard Cite

Widespread seepage of methane from seafloor sediments offshore Svalbard close to the landward limit of the gas hydrate stability zone (GHSZ) may, in part, be driven by hydrate destabilization due to bottom water warming. To assess whether this methane reaches the atmosphere where it may contribute to further warming, we have undertaken comprehensive surveys of methane in seawater and air on the upper slope and shelf region. Near the GHSZ limit at ∼400 m water depth, methane concentrations are highest close to the seabed, reaching 825 nM. A simple box model of dissolved methane removal from bottom waters by horizontal and vertical mixing and microbially mediated oxidation indicates that ∼60% of methane released at the seafloor is oxidized at depth before it mixes with overlying surface waters. Deep waters are therefore not a significant source of methane to intermediate and surface waters; rather, relatively high methane concentrations in these waters (up to 50 nM) are attributed to isopycnal turbulent mixing with shelf waters. On the shelf, extensive seafloor seepage at <100 m water depth produces methane concentrations of up to 615 nM. The diffusive flux of methane from sea to air in the vicinity of the landward limit of the GHSZ is ∼4–20 μmol m−2 d−1, which is small relative to other Arctic sources. In support of this, analyses of mole fractions and the carbon isotope signature of atmospheric methane above the seeps do not indicate a significant local contribution from the seafloor source.

show abstract

“…Modern seep activity can be detected through seabed observations, pore water analysis, methane anomaly detection, and many other methods (Borowski et al, 1996(Borowski et al, , 1999Borowski, 2004;Newman et al, 2008;Bayon et al, 2009bBayon et al, , 2011Mazumdar et al, 2012aMazumdar et al, , 2014Brothers et al, 2013Brothers et al, , 2014Lemaitre et al, 2014;Skarke et al, 2014), but temporal variations in methane flux in the past are not well constrained because it is difficult to select the appropriate indicators in quantifying and age determining the occurrence of seep activity. Consequently, little is known about the impact of methane seepage on the surrounding sediment environment in seep settings.…”

Section: Introductionmentioning

confidence: 99%